Phrase issued with sincerity or with sarcasm to respectively either acknowlege one's inability to be of further assistance, or to defend one's position as an asshole. Counter to doing nothing.

Sincerely: "He was thrown from the car and landed in a bloody heap in the curb. I'm not a paramedic - I didn't know what to do, so I dialed 911. It was the least I could do."

Sarcastically: "Yeah, the guy who owed me $1,000 was on the casino cruise. He was drunk and said he didn't have my money - again. Too bad the poor bastard tripped and fell over the railing. I thought I threw him a life saver, but it was an anchor. Hey, at least I tried... It was the least I could do."